Mass of MnO2 = 25 g
The reaction would be 3MnO2 + 4Al --> 3Mn(s) + 2Al2O3
Molar mass of Al = 26.982 g/mol
Molar mass of MnO2 = 54.938 + 2(15.999) = 86.936 g/mol
Calculating the moles = 25 / 86.936 = 0.2876 mol.
Mole ratio MnO2 and Al considering the equation = 3 mol of MnO : 4 mol of Al
Calculating the moles of Al = 0.2876 mol MnO2 x (4 mol of Al / 3 mol of MnO)
Number of moles of Al = 0.3834
Getting the mass in grams as asked = 0.3834 mol x 26.982 g/mol = 10.34 grams.
#6).
Every 1,000 mL makes 1 L
How many 1,000mL are there in 2,800 mL ?
That's division.
(2,800 mL) / (1,000 mL) = <em>2.8 L</em>
#7).
The 'perimeter' means the 'distance all the way around'.
You have to know that both sides of a rectangle are the same length,
and also the top and bottom are the same length.
So the perimeter of this rectangle is
(2 yd) + (4.5 yd) + (2.yd) + (4.5 yd) = 13 yd .
Oops. The problem wants to know the perimeter in feet.
So you have to know that each yard is the same as 3 feet.
In order to find the number of feet in 13 yards, you have to
take 3 feet 13 <em><u>times</u></em> .
(3 feet) times (13) = <em>39 feet .</em>
#8).
For this one, you have to know that every 36 inches makes 1 yard.
How many 36 inches are there in 48 inches ?
That's division.
(48 inches) / (36inches) = <em>1 and 1/2 yards</em> .
#9).
For this problem, you have to know how to handle a mixed number,
and you also have to know that there are 16 ounces in 1 pound.
Add up the fruit:
(3-1/2 pounds) + (4 pounds) + 2 pounds) = <em><u>9-1/2 pounds</u></em>
Now, remember that each pound is the same as 16 ounces. So if you
want to find the number of ounces in 9-1/2 pounds, you have to take
16 ounces 9-1/2 times .
(16 ounces) times (9-1/2) = <em>152 ounces</em>.
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#10).
This one is just adding up some numbers. But after you finish doing that, you have to know that 1,000 meters is called '1 kilometer' .
Add up the distances that Omar ran:
(1,000 meters) + (1,625 meters) + (1,500 meters) = <em><u>4,125 meters</u></em>
The problem wants to know how many kilometers this is, so you have to figure out how many '1,000 meters' fit into 4,125 meters.
That's division.
(4,125 meters) / (1,000 meters) = <em>4.125 kilometers</em>
Orbital
All atoms have the same number of electrons as protons. Negative electrons are attracted to the positive nucleus. This force of attraction keeps electrons constantly moving around the nucleus. The region where an electron is most likely to be found is called an orbital.
Here you go :)
